Micro-shutters have been used within the prior art as spatial light modulators. One of the more notable of these is U.S. Pat. No. 5,784,189 issued to Bozler et al. and assigned to Massachusetts Institute of Technology (MIT), hereinafter referred to as the Bozler '189 patent. This prior art disclosure taught making spatial light modulators using micro-shutters that were lithographically generated and electrostatically controlled. The individual micro-shutters employed aluminum and require electrostatic control. While useful as teaching a method towards fabricating light modulation devices with small apertures, the Bozler '189 fails to teach micro-shutter fabrication techniques that are useful under magnetic control.
Electrostatically controlled micro-shutters require additional processing steps to ensure that the moving micro-shutter element and its complementary electrode remain insulated from one another. Also, electronics of some sophistication is needed to address and actuate individual micro-shutter elements.
Magnetically controlled micro-shutters have the ability to respond to magnetic fields and as such do not require control electronics. Also, magnetic micro-shutters do not need to be insulated from a complementary electrode because no electrodes are required.
As shown in U.S. Pat. No. 4,012,828, a Digital Frame Counter is described where the exposures used for a camera are displayed in a digital format. Such a digital frame counter could be a Liquid Crystal Display (LCD). The advantages of this type of display are that individual numbers can be larger than the above discussed rotating wheel, (no discussion has been made) and each frame number can be displayed without resorting to the use of dots as intermediate frame numbers. The disadvantages of this type of display are that LCD's are relatively expensive, require support electronics and can appear dark in low light situations due to their dependence on polarizing filters for them to function.
As seen by the foregoing discussion, it should be readily apparent that there remains a need within the art for a magnetically controlled micro-shutter that is inexpensive to fabricate.